Abstract: Sustained neuroinflammation & synaptodendritic injury are the two hallmark features underlying NeuroHIV. Factors contributing to these pathological changes include low-level residual HIV replication/HIV proteins and/or toxicity of cART itself. It is well-recognized that drug abuse, specifically cocaine abuse, is a common comorbidity of HIV infection. Intriguingly, cocaine has also been shown to exacerbate neuroinflammation either through its direct effects on immune cells, such as microglia and/or by decreasing the effectiveness of cART. It can thus be envisioned that within the CNS, combinations of HIV proteins, abused drugs and cART create a toxic milieu promoting exacerbated neuroinflammation and abnormal glial-neuronal cross-talk via the pro-inflammatory mediators. The detailed molecular pathways underlying the dysregulated neuroimmune signaling and subsequent synaptodendritic injury, however, remain elusive. Our preliminary studies have demonstrated that: 1) HIV TAT can increase microglial activation via the NLRP3 inflammasome signaling; 2) cocaine activates microglia via the dysregulated autophagy pathway, & 3) Combination of clinically used antiretroviral cocktail (TFV, FTC, DTG) impaired microglial lysosome functions leading to their activation. Furthermore, we also demonstrated that IL1?, product of the NLRP3 inflammasome activation pathway, upregulated the glutamate receptor ionotropic NMDAs (GRINS) and concomitantly decreased spine density in primary neurons. The premise of this application thus is that combinations of HIV TAT, cocaine & ARVs can activate microglia via the NLRP3 inflammasome & autophagy pathways, and that the increased release of IL1?. In turn, contributes to neuronal dysfunction. Using both in vitro and in vivo (HIV transgenic rats) approaches we will test the hypothesis via three specific aims - SA1: Investigate the molecular mechanism(s) underlying TAT, cocaine, & ARVs (3 drug regimen)-mediated activation of microglia in vitro; SA2: Investigate the molecular mechanism(s) underlying IL1?-induced neuronal excitotoxicity & SA3: Validate in vivo the changes in NLRP3 inflammasome and autophagy signaling and also lncRNA malat1/NF-?B/GRINs axis in conjunction with behavioral deficits in HIV-Tg rats administered cocaine and cARV. Two experienced PIs (Drs. Guo & Buch) will co-lead this project to accomplish the proposed goals. This R01 application, in response to RFA-MH-18-610 titled ?Altered neuronal circuits, receptors and networks in HIV-induced Central Nervous System (CNS) dysfunction,? aims to explore the molecular mechanisms underlying how the dysregulated neuroimmune signaling caused by HIV proteins, drugs of abuse, & cRAT impacts the function of neuronal receptors.